1 



I 



400 r 



300 



200 



100 







800 



100 







I 



600 



400 



200 - 



C = control 

 LF = 6 g/m^/wee 

 HF= 25 g/m ? /we 

 XF= 7S o/m J /„, 



_L 



M 



J A 



MONTH 



100 200 



Annual Nitrogen Input gN/m 2 



Sewage sludge used as fertilizer 



Figure 30. Responses of two species of 

 marsh grass to rates of nitrogen fertili- 

 zation. The response of Spartina levels 

 out at about the dosage used in LF plots, 

 while the response of D i s t i c h 1 i s continues 

 to rise to the highest rates of N addition 

 used in XF plots. (Valiela and Teal, 

 unpubl. data, Great Sippewissett Salt 

 Marsh, MA). 



TettigonildS = grasshoppers 



NoduidS - moth larvae 

 \ I FulgOridS = plant hoppers 

 I I MlridS- plant bugs 



Figure 29. Abundance of herbivorous 

 insects in Great Sippewissett Salt Marsh 

 control and fertilized plots. Samples 

 were taken with a sweep net (data from 

 Vince 1979). 



fed upon by a chrysomelid beetle, 

 Erynephala maritima , and was replaced by 

 invading rhizomes from the surrounding 

 Spartina (Figure 32; Valiela et al. 1982). 

 Interestingly, the Sal icornia could 

 survive at the lowest tidal levels because 

 the beetle does not do well if submerged 

 too much. 



Probably most New England salt 

 marshes are polluted to some extent, if 

 only by pollutants carried in the air and 

 coastal waters. In the vicinity of 

 cities, some are heavily polluted. But 

 aside from repeated heavy oiling, digging, 

 and filling- in, salt marshes seem to 

 survive most human insults rather well. 

 In all of the experiments in Great 



1 2 

 08 



XF 75 g/m 2 /week 



HF - 25 g/m 2 /week 



8 g/m 2 /week 



control 



4 Qve std error 



2 



1. 08- 



U +P 



u 

 c 



urea . phosphorus 



urea 



control 



2 4 6 8 10 12 



YEARS 



Figure 31. Long-term effects of fertili- 

 zation regimes on the annual aboveground 

 peak biomass of Spartina alternif lora . 

 Standard errors omitted for clarity. 

 Control sewage sludge fertilizers, LF and 

 HF and urea at nitrogen level equal to HF 

 were started in 1970; XF in 1974; and U+P 

 at a level equal to HF in 1975. All are 

 graphed according to years from initiation 

 of experiment to facilitate comparisons 

 (Teal and Valiela, unpubl. data, Great 

 Sippewissett Salt Marsh, MA). 



50 



